E. O. Wilson's Darwinian Ethics of Natural Law

In Consilience, Edward O. Wilson recognizes that crucial for his unification of all knowledge is a biological account of ethics as rooted in evolved human nature. He rightly notes that in doing this, he is following in the tradition of naturalistic ethics that stretches from Aristotle to David Hume to Adam Smith and, finally, to Charles Darwin. He is also right to see this naturalistic tradition of ethics as being "empiricist" in contrast to the "transcendentalist" ethics of those thinkers like Immanuel Kant who look to a transcendent realm of moral freedom beyond the natural world of human inclinations and experience. But in rejecting Thomas Aquinas's natural law ethics as transcendentalist, Wilson fails to see the common ground shared by Thomistic natural law and Aristotelian natural right.

Wilson shares with Aquinas--and Aquinas's teacher Albert the Great--the belief that nature is a rational order of causal regularities that can be understood by human observation and reasoning. This scientific study of nature includes biology--as manifested in Albert's zoology, which continued Aristotle's biology and passed it on to Aquinas. Just as Albert and Aquinas sought to explain the natural moral law as rooted in human biological nature, Wilson wants to explain the natural moral sentiments as part of a comprehensive science of nature. Wilson's quest for "consilience" shows how the tradition of natural law reasoning can be extended and deepened through a modern science of human nature.

Human nature, Wilson insists, is not a product of genes alone or of culture alone. Rather, human nature is constituted by "the epigenetic rules, the hereditary regularities of mental development that bias cultural evolution in one direction as opposed to another, and thus connect the genes to culture" (164) For example, the rules of human language are not strictly determined by either genes alone or culture alone, but instead arise from the interaction of genetic mechanisms and cultural learning. Genes initiate a process of development that endows the human brain with neural mechanisms for acquiring language, so that in normal circumstances, a normal human child is prepared to learn whatever language in spoken in the social environment. Despite the diversity of human languages as shaped by diverse cultural traditions, there is a natural pattern of regularities: all normal human beings are prepared to learn a language, and the languages that they learn have universal traits that reflect the human brain's adaptation for learning language (132-33, 161-63). Such regularities of gene-culture interaction are what Wilson means by "epigenetic rules."

The gene-culture coevolution of morality is similar to that of language. The genetic evolution of the human species has endowed human beings with an instinctive propensity to learn morality. Human morality shows universal patterns shaped by the natural desires that constitute human nature. But the specification of those patterns will be shaped by human cultural traditions and by individual judgments as constrained by both the natural desires and the cultural traditions. This similarity between morality and language as based on instinctive capacities for social learning is a fundamental theme in Marc Hauser's recent book--Moral Minds--surveying the evidence for the biology of morality. My blog post on Hauser can be found here.

Wilson argues that since morality is ultimately rooted in the moral sentiments of human nature, a natural science of morality requires a biology of the moral sentiments. Although Wilson concedes that we are a long way from achieving such a biology, he has repeatedly throughout his writings used Edward Westermarck's Darwinian theory of the incest taboo as the prime example of how biology can explain the moral sentiments. My blog post on Westermarck's theory can be found here.

All moral rules might ultimately be explained in the same way that Westermarck explains the incest taboo. Morality, at the deepest level, depends on gut feelings that some things are right and others are wrong. The precise content of these feelings depends on what human beings learn through social experience, and this experience varies greatly across different cultural traditions. Yet the regularities in these moral feelings manifest the natural inclinations of a universal human nature that is prepared to learn some things more easily than others.

Wilson argues that social cooperation was advantageous for survival and reproduction during the evolutionary history of intelligent social animals like human beings. Natural selection favored those genetically heritable dispositions that promoted cooperative behavior, which included innate propensities to social emotions such as sympathy, love, guilt, shame, and indignation. Eventually, the highly developed intellectual faculties of human beings allowed them to formulate customary norms of conduct that expressed these social emotions of approval and disapproval. For example, the natural dependence of children on adults favored the emotional attachment of parent-child bonding. This dependence came to be expressed as social rules approving of parental care and disapproving of parental neglect. Similarly, the benefits of cooperating for mutual advantage in evolutionary history favored dispositions that enforce reciprocity--emotional approval of fairness and emotional disapproval of cheating. The innate disposition to learn such emotions would then be expressed as social rules that rewarded cooperators and punished cheaters.

Citing the research of neurologists like Antonio Damasio, Wilson infers that the innate propensity to experience moral emotions, which has been shaped by natural selection, is etched into the neural circuitry of the human brain (112-15). To live successfully as social animals, human beings must make practical decisions guided by the emotional control centers of their brains. Our brains incline us to feel sympathy and concern for the pleasures and pains of others, to feel love and gratitutde toward those who help us, to feel anger and indignation toward those who harm us, to feel guilt and shame when we have betrayed our family and friends, and to feel pride and honor when others recognize our good deeds. Insofar as these moral emotions are felt generally across a society, they support seocial rules of love, loyalty, honesty, and justice.

It might be, however, that a few human beings suffer from abnormal circuitry in their brains that prevents them from feeling, or feeling very strongly, the moral emotions that sustain morality. This seems to be the case for psychopaths, who feel no obligation to obey moral rules because they apparently do not feel the moral emotions that support such rules. If so, we must treat them as moral strangers (as I suggest in my chapter on psychopaths in Darwinian Natural Right).

If we saw Wilson's biology of moral sentiments as part of the natural law tradition, we might see that much (if not all) of what Aquinas said about the natural inclinations supporting natural law would be confirmed by modern biological research. For example, we might conclude taht the biological study of the social bonding between male and female and between parents and children provides a modern, scientific way of understanding what Aquinas identifies as the natural inclinations towards conjugal bonding and parental care. Aquinas's reasoning about marriage--that monogamy is completely natural, polygyny only partly natural, and polyandry completely unnatural--makes sense in the light of modern biological theories of human mating and parenting. Aquinas explained the natural inclinations by appealing to Aristotle's biological account of human nature compared to the natures of other animals. Wilson's biology of the moral sentiments continues in that same tradition of Aristotelian biological naturalism.

Wilson is certainly right in thinking that Aquinas regards the natural law as ultimately an expression of God's will, because he believes in God as the Creator of nature. But Wilson is wrong in thinking that Aquinas must therefore be an ethical "transcendentalist" who believes that moral knowledge comes only from some supernatural source beyond the natural experience of human beings. After all, Aquinas distinguishes the natural law, as known by the human mind's grasp of the natural inclinations, from the divine law, as known by God's revelation of His will through the Bible. Natural law conforms to the natural ends of human beigns as directed toward earthly happiness. Divine law, by contrast, conforms to their supernatural ends as directed toward eternal happiness.

Aquinas contends that the "moral precepts" of the Mosaic law--such as the rules against murder, theft, and adultery--belong to natural law, and, consequently, that they can be known by natural experience even without being revealed as divine commandments. These precepts belong to natural law, Aquinas says, because they derive their force from "natural instinct." The Mosaic law incorporates natural law insofar as it secures the conditions for satisfying the natural human desires for life, sexuality, familial bonding, and social order generally. Unlike the moral precepts, the "judicial" and "ceremonial" precepts of Mosaic law--such as the Jewish dietary restrictions and procedures of worship--could not have been known if they had not been revealed as divine law. These precepts derive their force from being instituted for the people of Israel. Before they were instituted, it was arbitrary whether the matters covered by these precepts were arranged in one way rather than another.

The contrast between Aquinas's "empiricist" view of natural law and his "transcendentalist" view of divine law is clear in his account of marriage. Aquinas believes that marriage belongs to natural law insofar as it serves two natural ends--the parental care of children and conjugal bonding. A Darwinian scientist like Wilson can accept this moral claim because it depends upon the observable nature of human beings. Aquinas believes, however, that marriage also serves a supernatural end that goes beyond natural experience. As a sacrament of the Catholic Church, marriage symbolizes the supernatural mystery of Christ's union with the Church. If this religious doctrine strenthens the marital commitment of those who believe it, then it reinforces the natural moral sense associated with marital bonding and thereby promotes the earthly happiness of human beings. Yet the sacred meaning of the doctrine points beyond nature to the eternal happiness that Aquinas believes to be the final end of human longing. This sacred meaning of marriage comes from a divine law that transcends human understanding and is beyond the realm of natural science. Yet the secular meaning of marriage comes from a natural law that can be known by natural experience and is open to scientific study. This secular meaning is compatible with Wilson's "empiricist" view of morality.

This should allow proponents of Aristotelian and Thomistic ethics to see Darwinian science as providing a scientific foundation for their ethics. One can see this, for example, in the writing of Alasdair MacIntyre. In his After Virtue (1981), he defended an Aristotelian and Thomistic account of morality as rooted in the moral and intellectual virtues, but he rejected any appeal to Aristotle's biology. Some years later, however, he indicated in Dependent Rational Animals (1999), that he had changed his mind--partly through reading my Darwinian Natural Right--because he had concluded that his Aristotelian/Thomistic ethics could be rooted in a Darwinian account of evolved human nature.